1. Field of the Invention
The present invention relates to a resin-encapsulated semiconductor device and a method of manufacturing the same and, more particularly, to a resin-encapsulated semiconductor device made by stacking a resin film to attain a low profile of a semiconductor package and a method of manufacturing the same.
2. Description of the Prior Art
Conventionally, a semiconductor device has its entire structure encapsulated or sealed with a resin mold, thereby preventing damages or ensuring sealing properties. In a conventional general resin-encapsulated semiconductor device, a semiconductor element is fixed to the die pad portion at the center of a lead frame. The electrode portion of the semiconductor element is adhered to the distal end portions of leads (i.e., inner leads) arranged around the die pad portion of the lead frame by using connector wire bonding, and the resultant structure is resin-molded. Normally, transfer molding using a mold is performed, and unnecessary portions of the lead frames are cut off, thereby manufacturing a semiconductor device.
However, a multi-pin package has a large wire length because of the limitation on the inner lead pitch. In the conventional technique, therefore, the wires are deformed by the resin flow in transfer molding of the resin, resulting in a short failure and a difficulty in attaining a low profile. In addition, the mold cost of transfer molding is high, and the effective resin utilization ratio is very low. For this reason, this method is not preferable from the viewpoint of decreasing the cost or saving the resources.
On the other hand, reductions in size and weight of electronic equipment have been strongly required in recent years. As packages suitable for thin devices represented by an IC card, COB or TAB are popularly used in which a bare chip is directly connected to a board and resin-encapsulated. These packages are generally manufactured by potting using a liquid resin.
In the prior art above, however, it is difficult to obtain a flat surface with a uniform thickness, resulting in a degradation in outer appearance. For this reason, a bore is formed at a predetermined portion of a board on which a semiconductor chip is to be mounted. A liquid resin is dropped in some excessive amount on the bore and cured in a heaped-up state. Subsequently, the extra cured resin portion is removed by polishing. However, this method poses problems of a decrease in productivity, a deterioration in reliability of the semiconductor chip due to a crack in the encapsulating resin, and the like.
A structure for mounting a chip on a board by the flip chip scheme has been proposed in Japanese Laid-Open Patent Publication No. 4-345041 in which a chip and a board are connected through an insulating film having a plurality of through holes and consisting of a resin with heat-fusion properties. However, to satisfactorily tightly adhered the chip to the board through the resin film, the resin must be actively flowed, and a positional shift tends to occur. Conversely, if the flow is insufficient, no satisfactory tight adhesion can be obtained.